Genomic DNA undergoes spontaneous base loss and deamination, followed by base removal. These are the leading causes for abasic site formation. The open-ring form of abasic ribose contains reactive aldehyde group that readily interacts with amines, occasionally leading to the formation of Abasic Site DNA interstrand crosslinks, known as Ap-ICL.
DNA crosslinks are blocking DNA replication and may result in cell cycle arrest, cell death, or cancer. Various repair processes have evolved to combat the deleterious effects. Replisome arrest triggers a ubiquitylation of replicative helicases recruiting the NEIL3 glycosylase for the repair of Ap-ICL. However, the molecular mechanisms of recognition and removal of Ap-ICL by this atypical DNA glycosylase remain elusive.
In this study, we present the crystal structure of the glycosylase domain of NEIL3 bound to single-stranded DNA (ssDNA) and a set of biophysical experiments aimed at providing a more comprehensive understanding of the process of Ap-ICL removal. Additionally, we characterize the resulting product of Ap-ICL removal as a 3’-phosphate. Our findings also demonstrate that the reduction of the Shiff-base of the Ap-ICL either impedes/does not affect its removal. Collectively, our data shed light on the molecular details of how NEIL3 glycosylase binds to and prefers ssDNA, rendering it a unique member of the Fpg/Nei family.
*For detailed experimental data see poster of Andrea Hušková